Soon after Covid-19 lockdowns began, in some places, you could see the change in the air. In northern India, the Himalayas, normally concealed by haze, became visible for the first time in years. Other regions experienced similar dramatic improvements, with decreases in air pollution revealing clear city skylines all over the world, from Wuhan to Los Angeles.
In a recent study, a group of researchers from the U.S. and Italy has attempted to quantify how many lives were saved during lockdowns in Europe and China due to this reprieve. They found that this major, though temporary, improvement in air quality and reduction in fine particle pollution has prevented thousands of deaths. The study, published in The Lancet Planetary Health, also shows how reopening scenarios and new outbreaks might affect future air pollution-related deaths.
According to the State of Global Air 2020 report, air pollution was the fourth leading risk factor for early death last year, following dietary risks, tobacco and hypertension. Exposure to unhealthy levels of air pollutants over the years has been shown to lead to cardiovascular and respiratory diseases, diseases largely responsible for air pollution-related premature deaths. Even short-term exposure, over the course of days, can lead to or worsen allergies, asthma, and respiratory diseases. For those with heart disease, it can lead to arrhythmias, heart attacks and death.
One harmful form of air pollution is fine particulate matter, particles emitted by fires, power plants, industrial facilities and vehicles. These particles are 2.5 micrometers in diameter, about 30 times smaller than the width of a human hair. When inhaled, they can make their way into the lungs and bloodstream.
When the pandemic led to shutdowns that substantially reduced traffic and industrial activity, a global natural experiment began. An international research group of scientists from the University of Notre Dame and the Climate Modeling Laboratory at the Italian National Agency for New Technologies, Energy and Sustainable Economic Development analyzed air pollution readings at over 2,500 sites across Europe and China to see how lockdowns might have influenced concentrations of fine particulate matter, and how that might have affected related deaths.
They looked at daily average concentrations of fine particulate matter during Europe’s and China’s corresponding lockdown periods and compared those measurements to average particulate matter levels during the same periods in 2016-2019. In both regions, particulate matter was lower than normal during lockdown. The researchers then used those particulate matter levels and mathematical models to see how many deaths were prevented due to cleaner air.
“We were able to estimate how many people didn’t die because the [particulate matter] concentrations were lower compared to the normal conditions,” said Paola Crippa, the senior author of the study and assistant professor of engineering and civil and environmental engineering and Earth sciences at Notre Dame.
The air quality gains from Covid-19 public health measures might have averted 2,190 and 24,200 premature deaths in Europe and China, respectively. The researchers also found that China experienced a much more dramatic improvement in air quality than Europe, which they attributed to a greater share of China’s emissions stemming from industry and traffic, both heavily impacted by lockdowns.
Looking at average particulate matter levels for the years 2016-2019, and predictions for 2020 levels, the researchers estimated how many deaths could be avoided under different reopening scenarios. In their more intermediate scenarios, which resemble the current situation in the world, between 111,700-160,300 early deaths related to air pollution might be avoided in China, and 29,500 early deaths could be averted in Europe.
Even if the world had resumed business as usual right after the lockdowns ended, 74,600 deaths could have been averted in China, and 13,600 in Europe. At the other extreme, if the lockdowns continued for the rest of 2020, China would have seen 287,000 fewer air pollution-related deaths, and Europe would have seen 29,500 fewer.
“In their results, you see a decrease in emissions due in large part to the various global lockdowns, and those lower emissions led to lives saved,” said Christa Hasenkopf, founder and former CEO of OpenAq, a nonprofit that facilitates access to international air quality data, who was not involved in the study.
While the lockdowns were a major player in air quality improvement, other factors were at work, too. The researchers found that in Europe, variations in weather heavily influenced particulate matter concentrations, for example through storms recirculating the air, or a lack of such storms allowing pollutants to accumulate in stagnant air.
These lockdowns also didn’t close all pollution sources or diminish all pollutants. The State of Global Air report showed that levels of ozone actually increased during lockdowns. While the Covid-19 public health measures shut down industrial facilities, a main source of pollutants in China, agricultural and residential emissions account for a larger share of air pollution in Europe during the colder months. Covid-19 lockdowns only partially affected emissions from those sources.
“For air pollution, there's no silver bullet,” said Hasenkopf. “There's a need in any particular place to understand the sources and to mitigate that.”
Crippa hopes that her group’s study highlights the need for air pollution policies tailored to a region’s needs. “The measures will have to be tuned to the right sources,” she said.
“In highly polluted places, I think there's a lot of bandwidth to reduce pollution levels with existing technology or even yesterday's technology,” said Hasenkopf. “Studies like this or the experiences people have had during lockdowns in highly polluted places where the air improved can shine a light on the opportunity to have clean air.”